harpoon.Analysis
Class Context<E>

java.lang.Object
  harpoon.Analysis.Context<E>

public abstract class Context<E>
extends Object

A Context object is an opaque representation of a method's calling context, intended to make it easier to generalize across context-sensitive and context-insensitive analyses. The Context consists of the last n "objects" (call-sites or methods). Only two operations are defined: we can make a new (empty) context (with a factory; see for example the GenericContextFactory class), and we can create a new context by adding another element on to the end of an existing context. Context-insensitive analyses have a singleton Context object, which is returned unchanged by the addElement() call. Usually a n-level context will be created, where Contexts are represented by an n-tuple holding the last n items given to addElement() (last n method calls, call-sites, etc). Behind the scenes, it will often be desirable to keep a context cache to avoid creating more than one live object representing a given context.

Note that, for context-sensitive analyses, there remain two main flavors of contexts: caller-based, and call-site-based. A caller-based Context will pass an HMethod to addElement(), and will group together all call-sites in this method which share the same destination. A call-site based Context will pass a Quads.CALL (or similar IR object) to addElement(), to distinguish different call-sites leaving to the same destination method.

Version:

$Id: Context.java,v 1.2 2003/06/17 16:44:56 cananian Exp $

Author:

C. Scott Ananian <cananian@alumni.princeton.edu>

See Also:

GenericContextFactory

Field Summary

static Context	CONTEXT_INSENSITIVE
static Context	CONTEXT_SENSITIVE_1
static Context	CONTEXT_SENSITIVE_2

Constructor Summary

protected

Context()

Method Summary

abstract Context<E>	addElement(E o) Add a new element to the end of this Context, 'forgetting' about elements at the start of the Context if necessary.
abstract List<E>	asList() Return the elements of this Context as a tuple, as represented by an unmodifiable List.
boolean	equals(Object o)
int	hashCode()
String	toString()

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Field Detail

CONTEXT_INSENSITIVE

public static final Context CONTEXT_INSENSITIVE

CONTEXT_SENSITIVE_1

public static final Context CONTEXT_SENSITIVE_1

CONTEXT_SENSITIVE_2

public static final Context CONTEXT_SENSITIVE_2

Constructor Detail

Context

protected Context()

Method Detail

addElement

public abstract Context<E> addElement(E o)

Add a new element to the end of this Context, 'forgetting' about elements at the start of the Context if necessary. For context-insensitivity, this method should return this unmodified. Context-sensitive analyses may wish to implement a context cache. Or not. Depends on how long you're planning on keeping those Context objects around, don't it.

asList

public abstract List<E> asList()

Return the elements of this Context as a tuple, as represented by an unmodifiable List. This is to support interoperability between different Context implementations. The object passed to the allElement() call which created this Context will be the last element of the returned List.

The length of this List will usually be bounded by a small constant.

hashCode

public int hashCode()

Overrides:

hashCode in class Object

Returns:

asList().hashCode()

equals

public boolean equals(Object o)

Overrides:

equals in class Object

Returns:

true iff the asList() representations of the two Contexts are equal.

toString

public String toString()

Overrides:

toString in class Object

Returns:

asList().toString()